The winding of the rotor or stator by means of a continuous wire is habitually carried out phase by phase. For example, for a three-phase machine, the three phases will be wound one after the other, each phase being offset by one or more notches relative to the preceding one. For a double three-phase, the six phases are wound in the same manner one after the other. The wires which constitute each of the phases form axial undulations on each side of the rotor or stator, all of these axial undulations constituting a chignon.
The disadvantage of this type of winding is that the axial undulations of the first phase impede the insertion in the base of the notch of the following phase, and so on, the last phase being hindered by the axial undulations of all the preceding phases. The consequence is that the notches are not filled in an optimum manner, which detracts from the coefficient of filling of the said notches, and therefore the performance of the machine.
The other disadvantage of this type of winding is that the winding time depends on the number of phases to be wound: the larger the number of phases, the longer the winding time, and a double three-phase or six-phase will require twice as to produce as a simple three-phase.
For a stator the winding can be carried out flat or on a closed stator.
It is also possible to wind a plurality of turns of the stator, i.e. a revolution of the stator or rotor, onto a support or core comprising notches which are open to the exterior, then to insert the turns thus wound on the stator by thrusting by expansion the turns of the notches in the support towards the notches in the stator. The disadvantage of this method is that the size of the notches in the support in which the initial winding is carried out has a limited depth and width, since the support must have an outer diameter which is smaller than the inner diameter of the stator, in order to be able to be placed in the interior of the stator, and the number of notches in the rotor and the support must be identical. In addition, the smaller the stator, the larger the number of turns, and thus the more difficult it is for the core to contain them. The winding is thus carried out in several stages, the turns then being connected to one another in order to form a phase.